Asymptomatic Bacteriuria: Common Causes and How to Treat It

Asymptomatic bacteriuria can be detected in a urine test. Treatment may be necessary in exceptional cases.
Asymptomatic Bacteriuria: Common Causes and How to Treat It
Leidy Mora Molina

Reviewed and approved by the nurse Leidy Mora Molina.

Last update: 31 March, 2023

It’s possible for bacteria to live in the bladder without causing any harm or diseases. This condition, known as asymptomatic bacteriuria, is common in men and women worldwide. We’ll tell you the most common causes and how to deal with it.

Asymptomatic bacteriuria is the presence of colonies of bacteria of the same species in the urine. It’s also characterized by a total absence of symptoms. In general, the number of bacterial colonies should be greater than 100,000 per milliliter of urine.

This condition varies according to the age, sex, and health status of each person. It’s more common in pregnant women, older adults, and children and is detected by urine culture.

Common causes of asymptomatic bacteriuria

The growth of bacteria in the urine may spark fear in many people. However, this is only experienced by a small number of patients.

The most frequent cause is having a catheter or tube inserted in the bladder for a long time. Similarly, there are some situations that increase the incidence of bacteriuria:

  • Cancer
  • Pregnancy
  • Chemotherapy
  • Kidney transplant
  • Corticosteroid use
  • Retrovesical reflux in children
  • Acquired immunodeficiency syndrome (AIDS)
  • Invasive genitourinary procedures, such as a transurethral approach

Studies (in Spanish) show a higher prevalence of asymptomatic bacteriuria in sexually active women, as well as in diabetic patients or patients with neurogenic bladder.

A pregnant woman.
Pregnancy is a stage when bacteria are more likely to lodge in the bladder.

Why are there no symptoms in asymptomatic bacteriuria?

Despite what most people believe, having bacteria in the urine isn’t always accompanied by symptomatology. The most common reason for this is that some germs are unable to colonize and invade the bladder; therefore, they’re washed away when urinating. However, the colonies remain active because of their high reproductive capacity.

Similarly, the good condition of the immune system makes it possible to stop bacterial adherence and prevent the symptoms of an infection. In some people with neuropathy, there may be no perception of the inflammation and pain caused by urinary tract infection.

You may be interested in: 6 Remedies for Urinary Tract Infections

Diagnosis of bacteriuria

To detect asymptomatic bacteriuria, a urine culture, with subsequent microscopic evaluation, is necessary. In general, this test isn’t requested in people who have no symptoms of urinary tract infection, so its finding is usually incidental.

A special case is a pregnancy. Protocols have included a routine urine culture in each trimester so that asymptomatic bacteriuria can be detected.

Diagnosis of this condition requires one positive bacterial growth sample in men or two positive samples in women. A general urine test can report the presence of germs as follows:

  • Absent bacteria: no evidence.
  • Rare bacteria (+): 1 to 10 bacteria per field are observed.
  • Some bacteria (++): 4 to 5 bacteria per field.
  • Frequent bacteria (+++): up to 100 bacteria per field.
  • Abundant bacteria (++++): more than 100 bacteria.

Research suggests that a minimum of 100 colony-forming units (CFU) is required for the diagnosis of asymptomatic bacteriuria. On the other hand, in cystitis, more than 100 CFU are usually detected and in pyelonephritis up to 1000 CFU.

The treating physician should evaluate other values in the urine test to determine the person’s health status. Such is the case of the presence of leukocytes, pyocytes, and nitrites in the urine. Finally, a urine culture will give an accurate diagnosis of the number of growing colonies and the germ responsible.

Treatment of bacteriuria

Today, there are people who live for years with asymptomatic bacteriuria without any health complications. In most people with bacteria in the urine, without symptoms, no treatment is necessary.

The use of antibiotics without a prescription increases bacterial resistance, compromises the natural urogenital flora, and could increase the risk of future infections. In fact, studies (article in Spanish) have shown that antibiotic therapy in asymptomatic bacteriuria offers no improvement.

However, there are exceptional cases of bacteriuria without symptoms in which preventive antibiotic treatment is indicated:

  • During pregnancy
  • Within 30 days of a kidney transplant
  • As part of the preparation protocol for an invasive urinary tract procedure
  • In people with kidney stones and a history of frequent infections
  • In young children with retrovesical reflux
Older adults, diabetics and patients with bladder catheters don’t require treatment if there are no symptoms.
A woman with kidney stones.
Kidney stones favor urinary tract infections, so these patients do need to be treated with antibiotics.

You may be interested in: What Do Your Kidneys Do?

When to seek medical attention

In some people, asymptomatic bacteriuria may be a transitional state to a bladder, urethral, or kidney infection. For this reason, it’s essential to be attentive to symptoms that may show the need for medical attention, such as:

  • High fever and chills
  • Frothy or bloody urine
  • Difficulty and discomfort when urinating
  • Pain in the back or sides

Asymptomatic bacteriuria is not the same as an infection

Asymptomatic bacteriuria is a condition that shows there’s a growth of bacteria in the urine. It’s a harmless condition that doesn’t require treatment, except in special conditions, such as pregnancy. If you suspect a urinary tract infection, don’t hesitate to seek professional help as soon as possible.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • Wiley J, Sons. Antibióticos Para La Bacteriuria Asintomática. Revista Médica Clínica Las Condes. 2018;29(2):251-255.
  • Lozano J. Infecciones urinarias. Clínica, diagnóstico y tratamiento. Offarm. 2001; 20(3): 99-109.
  • Alarcón T, Justa L. Bacteriuria asintomática. Asociación Español de Pediatría. Protoc diagn ter pediatr. 2014; 1(1):109-117.
  • López-López, Almudena, et al. “Incidencia de la infección del trato urinario en embarazadas y sus complicaciones.” (2019).

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.